If you accidentally drove over more than 4 catseyes in a row they would explode. This was a very clever scheme invented to prevent Russian tanks from invading. Tanks were longer than 4 catseyes but cars were shorter, so wouldn't set off the landmine unless you went very fast.

Growing up in West Germany during the 70s and 80s I was already in total fear of the Red Menace by age 7, and this totally believable logic just heightened my paranoia.

My dad would take great delight in hitting three catseyes and then narrowly avoiding the fourth while I screamed myself into a catatonic state in the back seat...